The invention described herein relates generally to resonantly photo-pumped X-ray lasers, and more particularly to a novel X-ray laser in which the gains of several laser lines that lase from collisional excitations and recombination processes are enhanced by resonant photo-pumping.
The first operational laboratory X-ray laser, which used collisional excitation as the pumping mechanism, was taught by Campbell and Rosen in U.S. Pat. No. 4,827,479 issued May 2, 1989. Moreover, this X-ray laser is also described by Rosen et al in Physical Review Letters 54, 106 (1985), with a discussion of the experimental demonstration of the laser provided by Matthews et al in Physical Review Letters 54, 110 (1985). This seminal work was also reported in Physics Today, March 1985, at pages 17 to 19. Additionally, a recent review of soft X-ray lasers is provided by Matthews and Rosen in Scientific American, December 1988.
The following are representative of the state-of-the-art in X-ray laser research and speculation: Cochran et al, in U.S. Pat. No. 4,803,687 issued Feb. 7, 1989, describe a sodium-neon laser target wherein Ne IX is (He-like Ne) resonantly photo-pumped by Na X (He-like Na). A carbon thermal buffer layer is required between the sodium and neon layers.
Hagelstein, in U.S. Pat. No. 4,660,203 issued Apr. 21, 1987, describes X-ray lasers wherein various multiply ionized species are used to pump high energy transitions in helium-like or hydrogen-like N, O, F, C or rare gases. The lasant material is located within a hollow container fabricated from parylene, or a material substantially transparent to radiation in the wavelength range from 60 to 300 Angstroms, and is multiply-ionized and undergoes at least one super-radiant laser transition.
Silfvast, in U.S. Pat. No. 4,592,064 issued May 27, 1986, discloses a scheme that permits high gain at visible and UV wavelengths in species such as Cd and Zn. A population inversion is established by producing a plasma that generates X-ray pulses in the 150 to 650 Angstrom wavelength range.
Elton, in U.S. Pat. No. 4,592,056 issued May 27, 1986, describes X-ray lasing systems wherein a neon-like sulfur plasma is used to pump a lithium-like neon plasma, and wherein a lithium-like silicon plasma is used to pump a lithium-like magnesium plasma.
Harris, in U.S. Pat. No. 4,380,072 issued Apr. 12, 1983, describes the method of exciting atoms to a storage level, then irradiating the excited atoms and thereby raising them to a higher level, whereupon the atoms lase to a lower level, other than ground, which is simultaneously emptied. This method results in the generation of XUV radiation.
Mani et al, in U.S. Pat. No. 4,229,708 issued Oct. 21, 1980, describe an X-ray laser wherein lithium-like atoms or ions are stimulated to lase by resonant or non-resonant antistokes Raman processes. The laser functions by directing filtered, black-body radiation in the soft X-ray region into a lithium-like vapor.
Jaegle et al, in U.S. Pat. No. 3,826,996 issued July 30, 1974, describe obtaining a medium having a negative absorption coefficient within the ultra-violet and X-ray range, by focusing a giant-pulse laser beam on an aluminum target.
Even though proposals have been made of many schemes using the resonant photo-pumping mechanism to drive various X-ray lasers, the fact is that the resonant photo-pumping mechanism has not as yet been actually demonstrated in the X-ray, or even the soft X-ray, region. The shortest wavelength at which significant gain has been measured using resonant photo-pumping is 2163 Angstroms in beryllium-like carbon pumped by a manganese plasma, in work reported by Qi and Krishnan, Phys. Rev. Lett. 59, 2051 (1987).